The steep walls of Lua Poholo pit crater, immediately NE of Mokuaweoweo caldera, expose a small portion of the massive pile of thin, overlapping lava flows that have construced the Mauna Loa shield volcano. This view from the NE shows the rim of Mokuaweoweo caldera at the upper right. Lava flows from recent eruptions, including the last eruption of Mauna Loa, in 1984, fill the floor of the pit crater.
Hawaiian Volcano Observatory scientists conduct an electronic-distance measurement (EDM) survey on the rim of Kilauea caldera in 1987, with snow-capped Mauna Loa in the background. The procedure uses a laser beam, which is reflected back to the EDM instrument from a distant cluster of reflectors. A precise determination of the horizontal distance between the two points is made by a small computer in the EDM instrument. These measurements allow scientists to detect inflation of the volcano as magma rises to the surface prior to an eruption.
Hawaii's two largest shield volcanoes, Mauna Loa (in the background to the south) and Mauna Kea, have dramatically differing profiles. Mauna Loa, the world's largest active volcano, has the classic low-angle profile of a shield volcano constructed by repetitive eruptions of thin, overlapping lava flows. Mauna Kea is also a shield volcano formed in the same manner, but its profile has been modified by late-stage explosive eruptions, which constructed a series of cinder cones that cap its summit.
Mauna Kea (left) and Mauna Loa (right), both over 4000 m above sea level, are the world's largest active volcanoes, rising nearly 9 km above the sea floor around the island of Hawaii. This aerial view from the NW shows the contrasting morphologies of these two shield volcanoes. In contrast to the smooth profile of Mauna Loa, Mauna Kea's early shield volcano morphology is modified by the late-stage products of explosive eruptions.